Electrochemical Studies of Selected Lanthanide and Californium Cryptates.
Electrochemical Studies of Selected Lanthanide and Californium Cryptates.
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选定的镧系元素和锎穴状化合物的电化学研究。
DOI：
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发表时间：
2019
影响因子：
4.6
通讯作者：
T. Albrecht‐Schmitt
中科院分区：
文献类型：
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作者：
Matthew L Marsh;F. White;David S Meeker;Carla D McKinley;D. Dan;Cayla E Van Alstine;Todd N. Poe;Danielle L. Gray;D. Hobart;T. Albrecht‐Schmitt
定量还原溶液中CfIII → CfII的努力及其循环伏安法的研究受到以下因素的阻碍：其稀缺性，与操纵异常强烈的γ发射体相关的重大挑战，小反应规模，对非水溶剂的需求，以及其对配体和溶剂的辐射分解效应。在努力克服这些障碍，我们报告的稳定CfII封装在2.2.2-穴状配体和比较容易还原的镧系元素，Sm 3+，Eu 3+，和Yb 3+。循环伏安法测量表明，CfIII/II显示具有SmIII/II和Yb III/II特性的电化学行为。[Cf（2.2.2-crypt）]3+/2+和[Sm（2.2.2-crypt）] 3 +/2+的°E1/2值分别为-1.525和-1.660 V（相对于四氢呋喃（THF）中的Fe/Fe+）相似。然而，CfIII/II与2.2.2-穴状配体络合后的ΔE值与Yb III/II更接近，封装后的位移分别为705和715 mV，而SmIII/II的位移（520 mV）反映了EuIII/II的位移（524 mV）。这表明更多的结构相似性之间的CfII和Yb II的解决方案比与SmII，可能源于更相似的离子半径和本地的协调环境，一个假设，证实了晶体学和扩展的X射线吸收精细结构测量从其他系统。EuIII/II，SmIII/II和Yb III/II之间的竞争性离子结合实验也进行了，并显示出较不利的YbIII/II的结合。[Ln（2.2.2-穴醚）（THF）][BPh 4]2（Ln = EuII，SmII）的连接性结构表明THF在这些氧化还原反应中起重要作用。
Efforts to quantitatively reduce CfIII → CfII in solution as well as studies of its cyclic voltammetry have been hindered by its scarcity, significant challenges associated with manipulating an unusually intense γ emitter, small reaction scales, the need for nonaqueous solvents, and its radiolytic effects on ligands and solvents. In an effort to overcome these impediments, we report on the stabilization of CfII by encapsulation in 2.2.2-cryptand and comparisons with the readily reducible lanthanides, Sm3+, Eu3+, and Yb3+. Cyclic voltammetry measurements suggest that CfIII/II displays electrochemical behavior with characteristics of both SmIII/II and YbIII/II. The °E1/2 values of -1.525 and -1.660 V (vs Fc/Fc+ in tetrahydrofuran (THF)) for [Cf(2.2.2-crypt)]3+/2+ and [Sm(2.2.2-crypt)]3+/2+, respectively, are similar. However, the ΔE values upon complexation by 2.2.2-cryptand for CfIII/II more closely parallels YbIII/II with postencapsulation shifts of 705 and 715 mV, respectively, whereas the shift of SmIII/II (520 mV) mirrors that of EuIII/II (524 mV). This suggests more structural similarities between CfII and YbII in solution than with SmII that likely originates from more similar ionic radii and local coordination environments, a supposition that is corroborated by crystallographic and extended X-ray absorption fine structure measurements from other systems. Competitive-ion binding experiments between EuIII/II, SmIII/II, and YbIII/II were also performed and show less favorable binding by YbIII/II. Connectivity structures of [Ln(2.2.2-cryptand)(THF)][BPh4]2 (Ln = EuII, SmII) are reported to show the important role that THF plays in these redox reactions.